At present, the application range of liquid crystal compounds has expanded more and more widely, which can be used for various types of displays, electro-optical devices, sensors etc. The liquid crystal compounds for use in the above-mentioned display field are in a wide range of varieties, wherein the application in nematic phase liquid crystals is most extensive. Nematic phase liquid crystals have been used in passive twisted nematic (TN), super-twisted nematic (STN) matrix displays and systems having a thin filter transistor (TFT) active matrix.
With regard to the application field of thin film transistor techniques (TFT-LCD), although in recent years the market thereof has been very huge and the techniques also gradually become mature, the requirements on display techniques by people are also continuously increasing, especially in the aspects of achieving a quick response, reducing the driving voltage to reduce power consumption, etc. Liquid crystal materials, as one of important optoelectronic materials for liquid crystal displays, play an important role in improving the performance of liquid crystal displays.
As liquid crystal materials, they need to have good chemical and heat stabilities and stabilities to electric field and electromagnetic radiation. In addition, as a liquid crystal material for use in thin film transistor techniques (TFT-LCD), the material not only needs to have the stabilities as described above, but also should have the properties of a wider nematic phase temperature range, an appropriate birefringence anisotropy, a very high electrical resistivity, a good anti-ultraviolet performance, a high charge holding rate, a low vapor pressure etc.
With regard to the application in dynamic image display, such as a liquid crystal display television, in order to achieve a high quality display and eliminate the displayed image sticking and streaking, the liquid crystal is required to have a very fast response speed, and therefore the liquid crystal is required to have a lower rotary viscosity γ1; in addition, in order to reduce the equipment energy consumption, the driving voltage of the liquid crystal is expected to be as low as possible, so improving the dielectric anisotropy Δ∈ of the liquid crystal has an important significance for mixed liquid crystals.